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The study compared and contrasted cognitive and metacognitive reading strategies awareness and use of EFL students studying biology, business studies, information technology, engineering, and English in a higher education institution in Oman. It also examined the relationships among strategy preferences and discipline, gender and language proficiency. Quantitative data was collected from 375 students using Survey of Reading Strategies (SORS) and a background information questionnaire. Results from quantitative data reveal that there are no significant differences between students of various disciplines in terms of strategy preferences for metacognitive, cognitive and support strategies. Also, it was observed there is no significant relation between learners' self-perceived proficiency and their scores of SORS. However, differences were found in gender as female students used more strategies as compared to male students. Semi-structured interviews conducted with students from biology, business studies, information technology, engineering, and English disciplines revealed that learners were aware of metacognitive, cognitive and support strategies. But, strategy preferences of students at different proficiency levels were varied. For example, students who had rated their English proficiency as high did not preview a text before reading. In contrast, students who had rated their English proficiency as low were in favor of this strategy. Overall, this study contributes to existing literature and provides insight about strategy preferences of Omani students in different disciplines. An understanding of the similarities and differences of strategy preferences of Omani learners from different disciplines will help teachers and curriculum developers to develop their courses to suit the needs of the learners.

The thesis describes the synthesis of new analogues (53-57) of PBG and their inhibition of and mechanistic studies on the enzyme PBG deaminase from E. coli. The analogues with an additional alkyl group, 53 and 54, were successfully obtained in good yields in 10 steps. The caged compound 97 was also obtained but the final step of hydrogenolysis of the benzyl protecting groups also caused reduction of the nitro group on the 2-nitrobenzyl substituent. Testing of analogues 53 and 54 with the enzyme (PBGD), however, showed no inhibition. A new route for the synthesis of the conformationally restricted analogue 6, 11-ethanoPBG 56 was developed in this work and one stereoisomer of 56 was obtained (the cis-isomer). When this analogue was tested as an inhibitor it also showed no inhibition. This was thought to be due to the stereochemistry of the compound since modelling studies had predicted that the trans-isomer would bind tightly to the enzyme not the cis-isomer. Therefore, the 11-hydroxy-6,11-ethanoPBG analogue 57 was prepared and tested as an inhibitor with the enzyme. The result was only a modest effect on the enzyme's kinetics. 6-Methyl-PBG 55 which has the extra methyl group on the acetate side chain of PBG, was prepared to test the importance of this chain. When the compound was tested as an inhibitor of PBG deaminase it showed strong inhibition and a K1 value of about 3mM was determined. This is the strongest inhibitor ever obtained for the enzyme. When this analogue was tested as a substrate for the enzyme it appeared by UV/visible spectroscopy to form a novel porphyrin, although due to the small quantity, it was not possible to isolate this porphyrin. In addition, it was possible to isolate the covalent enzyme/analogue complexes by the use of the FPLC technique. It was also possible to confirm the formation of complexes of the enzyme with one and two molecules of the substrate analogue bound for the first time by the use of the LC-mass spectrometry. This work also describes attempts to crystallise some of the enzyme/analogue intermediates, which were isolated by the FPLC. These attempts were successful and single crystals were obtained. These crystals diffract well and currently further work is going on to solve their structure. DesaminoPBG 26 has been previously prepared and gave a K1of 75 mM with PBG deaminase from human erythrocytes. In this project it has been tested with the PBG deaminase from E. coli and shown to be a less powerful inhibitor. A new approach for preparing 2,3-disubstituted pyrroles was developed and the 2-methyl-3-pentylpyrrole 59 was obtained in 70% yield. This compound is used as a building block in the biosynthesis of the red pigment prodigiosin 168, one of a class of naturally occurring polypyrroles which exhibit antimicrobial and cytotoxic properties.

Prenyltransferase (PT) biocatalysts are late-stage tailoring enzymes that modify natural products. PTs catalyze the attachment of prenyl moieties to natural product acceptors using pyrophosphate donors. This prenyl modification in small molecules leads to changes in structural and biological activities. Understanding the structural insights as well as the mechanisms by which PTs function allows us to utilize PTs as a unique approach towards drug development. PriB PT is an example of aromatic PTs that has been characterized previously as a L-tryptophan (L-Trp) C6 C-prenyltransferase (C6-C-PT). Analysis of PriB binding pocket, highlighted key residues that might play an important role in determining the regiospecificity of the enzyme and their mechanisms. Hence, we hypothesized that site-directed mutagenesis of one of these residues will alter the enzyme regiospecificity and/or its permissiveness leading to variation in the pharmacokinetics and biological activities of small molecules. Site-directed mutagenesis approach was used to engineer PriB PT as a model for C6-PTs and the purified mutant proteins were produced and purified. In vitro reactions of the purified engineered proteins have shown altered regiospecificity toward substrate acceptors when compared to wild type. The long-term goal for this study is to utilize the permissiveness of PriB enzyme for drug diversification and determine the activity of the mutant PriB enzymes. This study will also shed some light on the mechanistic insights of aromatic C6-PTs.

Industrial hygienists generally place air-sampling probes on the mid to upper torso of workers when attempting to determine inhaled concentrations. There is no convincing evidence that concentrations measured on the chest are equal to inhaled concentrations. To determine how well surrogate locations matched concentrations at the mouth (Cmouth), low concentrations of ethanol in nitrogen were released between the hands of standing and seated human subjects while they moved children's blocks back and forth over the source.;In all cases, each of four subjects stood or sat with their backs to the airflow in a wind tunnel because previous studies had established that facing downstream produced exposures that were more than 100 times the exposures when facing upstream or sideways to the flow with the source in the subjects' hands. Sampling probes were placed at the subject's mouth, nose, forehead, neck, both collars, center chest and both lapels. Airflow was drawn to 3L Teflon(TM) sampling bags at 0.15 Lpm. Concentrations were measured using a gas chromatograph with a photo-ionization detector, which was calibrated daily over the range of sample concentrations. Subjects were tested at wind tunnel cross-draft velocities of 11.3, 27.2, 47.5, 81.5, and 103.5 ft/min while either exhaling through a tube or not and either sitting or standing.;The results showed that posture and wind tunnel velocity have highly significant effect on sampling location concentration (p< 0.01). Exhaling through a tube was less important (p< 0.04). As with a previous manikin study, concentrations varied in an inverted-V with velocity. Concentrations across the chest were as much as 22% higher than Cmouth when seated and 70% higher than Cmouth when standing. Concentrations at the neck and collar were much closer to Cmouth but still deviated by as much as 10%. Levels at the forehead were generally lower than Cmouth but were highly correlated to it. Levels adjacent to the tip of the nose deviated the least 7%, as might be expected. Based on the study, the best surrogate to mouth location are the collars with an over estimation of 7%.;Previous studies raise strong concerns about the accuracy of samples taken anywhere below the collar when the subject is close to the source and airflow is from the rear. The dramatic effects of posture on concentrations suggest that exposure studies should include both sitting and standing as well as variations of each. The effects of body size and shape and hair length should be investigated in future studies.